765 square miles have already burned, that's twice the size of new york city. crews have been fighting the blaze for nearly a month but it is only 21% contained. nearly 800 structures have been destroyed, another 16,000 are threatened. related to that, a new and comprehensive study by the united nations warns that the wildfires, floods and excessive heat consuming parts of our planet could have catastrophic results unless nations act fast to stop greenhouse gas emissions. scientists make it clear humans are to blame. cbs' ben tracy reports. >> reporter: this summer's apocalyptic wildfires in california and greece, floods in belgium are just a glimpse of couldome. scisay thelanet isn at time in at least 2,000 years. >> climate chang a proem that is here now.no'se,nd igefat >> reporter: the un. report